Unless countermeasures are taken, in a cold climate, water conduits, especially in commercial aircraft, can freeze at high altitudes or when the aircraft is parked. For this reason it is necessary to heat or to drain these water conduits. For heating, as a rule, heating strips may be used which can, for example, comprise two electrical conductors, a semiconductor situated in between, and an insulation layer, which heating strips in several sections are installed parallel to the conduits. Materials used include, for example, cellulose with PVC coatings. At least some of these materials may not be self-extinguishing or they may be toxic and smoke-emitting. Furthermore, the cellulose materials may be hygroscopic.
Due to their limited bending radius, the relatively high temperature on the narrow surface (approximately 1 cm width), their movement limits in the three spatial directions, their relatively substantial thickness, their relatively heavy weight, the type of attachment and connection, FEP heating strips may be associated with certain disadvantages when compared to flexible heating elements. Resistance heaters may comprise wires or foils and which in the positive and in the negative temperature ranges have identical rated outputs, in other words constant resistance, and therefore because of the different local temperature profile may require individual control circuits in the aircraft. DE 197 26 419 A1 and U.S. Pat. No. 6,126,483 describe heat-conductor connection systems in an aircraft, which is hereby incorporated in its entirety by reference.